1. Field of the Invention
The present invention relates to a toe-piece for binding a boot on a gliding board adapted for the practice of ski touring.
2. Description of Background
There exist toe-pieces equipped with devices adapted to the practice of ski touring practice, whether in the ascent phase or in the descent phase.
For example, U.S. Pat. No. 8,544,869 discloses a first conventional boot-fastening mechanism dedicated to the ascent. The latter comprises boot-fastening mechanisms defining a hinge axis about which the boot pivots when engaged with this mechanism. During descent phase, this mechanism is reinforced by a second mechanism covering the front portion of the boot. This second mechanism comprises a jaw comprising two wings and a longitudinal support surface. The jaw is movable between an active position, in which it is in contact with the boot, and an inactive position, in which it is no longer in contact with the boot.
In this solution, the wings and the support surface form a single piece. With this integral construction, it is necessary to provide a large clearance at the front of the toe-piece for retracting the jaw to create a space in the area of the first mechanism, in order not to hinder the rotation of the boot during the descent phase. The jaw can retract only forwardly of the toe-piece due to its space requirement. This results in a relatively large toe-piece. Moreover, this construction does not allow relative movement between the wings.
For ski touring, a commonly used toe-piece is described in the document EP-A-0 199 098. This toe-piece comprises a boot-fastening mechanism provided with two points capable of cooperating with an insert positioned on the front portion of the boot sole. Each point is attached to a first arm of a lever articulated about a longitudinal axis and extending substantially upwardly. The two levers are arranged symmetrically with respect to a vertical plane passing through the longitudinal axis of the toe-piece. The second arm of a lever extends toward the other lever and is substantially horizontal. The second arms of the levers are connected to the same central element by springs. When the fastening mechanism is activated, the common central element is lowered, thereby causing the pivoting of the levers so as to bring them closer to the points. The two points are then aligned and cooperate with the boot. The aligned points define a hinge axis of the boot, transverse to the gliding board.
During the ascent phases, it is preferable to block the pivoting of the levers in order to maintain cooperation between the points and the boot. Without this locking, the points may be spaced apart, causing the release of the boot from the toe-piece. Locking mechanisms are described in the documents EP-A-2 347 807 and EP-A-2 452 731. In these examples, the locking mechanism immobilizes an actuating lever acting on the common central element of the levers.
Due to these constructions, the points exert substantial forces on the boot when the latter is engaged with the toe-piece. These forces can cause wear on the boot in the area of the interface, on the one hand, and disturb the rotation of the boot about of the pivot axis, on the other hand. Indeed, the greater the force exerted by the points, the more rubbing/friction is generated during the rotational movement of the boot. It is therefore desirable that less force be exerted by the points on the boot to facilitate the rotation of the boot about a transverse axis.
Moreover, when a lateral force is exerted on the front of the boot, these forces are transmitted by the levers to the central element. The take-up of lateral forces is not direct with the chassis. The levers are substantially constrained, thereby implying adapted dimensioning which tends to weigh down the structure. Furthermore, the immobilization of the levers is obtained via a long driveline. The functional or wear clearances between the elements do not promote good control of the gap dimension of the points.
The ascent phase during ski touring requires a binding of the boot to the ski that is functionally very different from that required in the descent phase. This translates into requirements in terms of safety and retention of the binding and kinematics of the boot, which are variable from one phase to the other. Thus, during the descent, the binding must ensure very good boot retention on the ski, preferably with binding release in the event of a fall in order not to injure the skier. During the ascent, the boot must be capable of rotating about a transverse axis substantially at the front of the boot sole. Therefore, the boot is not immobilized in relation the ski, and there is no need for binding release in the ascent.
A number of bindings have been designed specifically for the descent. Such bindings often comprise a toe-piece incorporating a lateral release mechanism associated with the pivoting of wings adapted to clamp the front of the boot. Such a toe-piece is described in the document FR-A-2 089 540.
With respect to the ascent, the toe-piece described in the above-mentioned document EP-A 0 199 098 refers to the practice of ski touring. This solution includes a boot-fastening mechanism defining a hinge axis about which the front of the boot pivots during the ascent.
Due to the various functional needs during practice of ski touring, certain manufacturers have developed toe-pieces supporting two distinct front boot-retaining devices. Thus, the skier may use a retaining device adapted to each respective ascent or descent phase of ski touring. The document EP-A-2 626 116 illustrates a toe-piece of this type. This solution includes a first front boot-retaining device provided for the descent and comprising two pivotable wings associated with a lateral release mechanism. The wings support interface surfaces adapted to come into contact with the front a boot sole in order to vertically and laterally maintain the front of the boot. This toe-piece also includes two points, each being fixed on a respective extension of a wing, above the interface surfaces. These points constitute elements of a boot-fastening mechanism similar to that described in the document EP-A-0 199 098. In the embodiments described in the document EP-A 2 626 116, the points define a boot hinge axis positioned longitudinally, substantially in the area of the interface surface used as a longitudinal abutment for the boot, when the toe-piece is in the descent configuration. This arrangement reinforces the longitudinal compactness of the toe-piece. To optimize the toe-piece, each point is integral with a wing. Thus, these points are directly biased by the lateral release mechanism. The number of constituent elements is reduced. Although compact lengthwise, this construction causes an upward offset of the boot hinge axis during the ascent phase. Consequently, the front of the boot pivots about an axis of rotation distant from the gliding surface of the ski when the toe-piece is in the ascent configuration. However, to improve the stability of the skier and preserve the equipment during the ascent phases, the axis of rotation of the boot is preferably as close to the gliding surface as possible. The previous construction does not make this possible and imposes a minimum height dimension corresponding to the space requirement of the elements of the first front retaining device.
Furthermore, due to their positioning, the points are relatively exposed/accessible and may catch and/or injure to the user while handling the ski when not in use.